Over the past 5 years the laboratory of the applicant has been studying the effects of hormones on gastrointestinal absorption of dietary amino acids and sugars using epithelial cells of the teleost intestine. A variety of experimental approaches to this problem have been used during this period including electrophysiology, cell suspensions, purified vesicle techniques, and cell culture. All these studies have provided some insight into how a specific vertebrate hormone enhances the transintestinal absorption of a specific nutrient. To date, however, a complete picture of this mechanism is not available for any solute or any hormone in the lower vertebrates. The proposed investigation will use the combination of membrane vesicle techniques and epithelial cell culture procedures to ascertain how at least two hormones, insulin and alpha-methyltestosterone, influence the transintestinal absorption of a sugar, an amino acid, and a short chain fatty acid. To accomplish these goals, purified brush border membrane vesicles will be prepared according to standard methods we have employed for the last 10 years. These vesicles will be used to measure the properties of solute transport across this membrane in response to hormone stimulation. In addition, confluent epithelial monolayers grown in cell culture will be used to expose the intestinal cells to the respective hormones for predetermined times before assessing the possible effects of this exposure to transcellular movements of each organic solute. These studies taken together should allow us to determine the specific cellular and membrane effects of each hormone on the absorption of the selected dietary constituents.